I think we're thinking of different use cases and therefore talking past one another. My SPARQL usage was not using an rdbms under the covers and was explicitly

I think we're thinking of different use cases and therefore talking past one another. My SPARQL usage was not using an rdbms under the covers and was explicitly using RDF data. Querying triple data in SQL would be quite clumsy except in the simplest usages, hence the existence of SPARQL. I have seen the libraries that can run SPARQL against an rdbms (for example the 3 or 4 column indexed table that would represent triples or quads). I would imagine performance would be an issue there--but for me rdf has mainly been around aggregating and exploring data, if I need to scale to massive queries per second I'd use something else.